Hot wire igniter

ABSTRACT

A hot wire igniter for igniting a gas appliance is disclosed. The coil of the hot wire igniter is formed from a thin high temperature, iron, chromium, aluminum alloy having a center section that is tightly wound. Alternatively, the coil can be formed from an alloy of platinum and iridium, or a similar high temperature metal alloy. The coil turns initially do not touch one another and each end of the coil is welded to a lead-in rod that is received within an insulator member. The lead-in rods are connected to a power source. The coil portion of the hot wire igniter is received within a gas collector box which is attached to the burner to be ignited. Application of the voltage source to the lead-in rods causes the coil of wire to reach a temperature in excess of the ignition temperature of the gas-air mixture which surrounds same causing the ignition of the mixture.

TECHNICAL FIELD

The present invention relates, in general, to an igniter and, moreparticularly, to a hot wire igniter that can be used for the ignition ofgas in any type of gas appliance.

BACKGROUND ART

Gas grills typically utilize propane gas, natural gas or some type ofmanufactured gas as their fuel source and a spark ignition system toignite same. Such a spark ignition system can be affected byenvironmental factors. For example, such a spark ignition system mayoperate erratically in a very damp and/or windy environment. Also, theoperation of such a spark ignition system can be adversely affected byorganic contamination from the foods being grilled. In addition, such aspark ignition system is noisy when actuated since it typically utilizesa piezoelectric type igniter that is mounted on a sheet metal panelwhich effectively transmits the igniter actuation noise into thesurrounding atmosphere. Furthermore, the positioning of the electricalwiring within the grill using a spark ignition system is critical sincethe heat generated within the grill might adversely affect the wiring.Also, due to the high frequency nature of the spark produced by suchignition systems, the positioning of the wiring within the grill canaffect the efficiency of the resulting spark. In addition, because suchspark ignition systems produce high voltages, any defects in the wiringor any deterioration thereof can adversely affect the resulting spark.In view of these disadvantages associated with spark ignition devicespresently utilized in gas grills, it has become desirable to developanother type of ignition device, such as a hot wire igniter, forigniting the grill.

A glow wire type ignition system is disclosed in U.S. Pat. No. 4,130,104(Kristen, et. al.), however, the application of the igniter disclosed inthis patent is for a gas stove, rather than a gas grill. In thisinstance, the glow wire type igniter is a replaceable component withinthe burner assembly for the stove and is comprised of an igniter wirefilament that is located within the flue and is positioned so as to bevisible through a display window. Electrical switching means areprovided to maintain the igniter wire in the glowing condition when theburner assembly is operating and to continue to maintain the igniterwire in the glowing condition whenever the burner surface has reached atemperature that exceeds a pre-determined level. In this manner, theigniter wire provides two functions, i.e., to ignite gas that emanatesfrom the burner and to provide an indication when the burner surfaceexceeds a pre-determined temperature. This type of glow wire typeignition system is not appropriate for a gas grill when the onlyfunction of such an igniter is to ignite the gas emanating from theburner within same.

A glow plug that concentrates its heat at the tip of the protectivesheath of the plug so that the tip of the plug is the first part of theplug to reach ignition temperature is disclosed in U.S. Pat. No.5,251,589 (Duba, et. al.). In this case, the heating element has acomplex shape since it is comprised of a helical shape portion having aplurality of constant diameter turns connected to a portion having moreclosely spaced turns of decreasing diameter. The outer end of theheating element is provided with a plurality of constant diameter turnsthat are in contact with each other. In addition to the structure of theheating element being quite complex, the glow plug disclosed in thispatent is for an internal combustion engine, rather than a gas grill.

An ignition and control system for a gas burner which includes both aceramic glow igniter and a hot-wire actuated switch that are connectedin series is disclosed in U.S. Pat. No. 3,776,684 (Wright). In thiscase, the ceramic glow igniter is typically constructed of siliconcarbide and is used in conjunction with the hot-wire actuated switch.The application of the ignition and control system in this patent is fora furnace, rather than for a gas grill.

A hot surface ignition system that utilizes a silicon carbide igniter isdisclosed in U.S. Pat. No. 4,976,605 (Geary). In this case, theapplication of the hot surface igniter is for a gas furnace, rather thana gas grill. A gas burner control system that utilizes a silicon nitridetype igniter is disclosed in U.S. Pat. No. 4,925,386 (Donnelly, et.al.). Here again, the application of this silicon nitride type igniteris not for a gas grill.

In view of the foregoing, it has become desirable to develop a hot wireigniter that can be utilized for the ignition of gas in any type of gasappliance.

SUMMARY OF THE INVENTION

The present invention overcomes the problems associated with utilizing aspark ignition device for igniting a gas appliance by providing a hotwire igniter that operates at a significantly lower voltage and highercurrent than presently available spark ignition devices. In addition,the lower voltage does not include a high frequency component. The coilof the hot wire igniter of the present invention is formed from a thinhigh temperature, iron, chromium, aluminum alloy having a center sectionthat is tightly wound. Alternatively, the coil of wire can be formedfrom platiniridium, which is an alloy of platinum and iridium, or asimilar high temperature metal alloy. Each end of the coil is welded toa lead-in rod that is enclosed within an insulator member. The lead-inrods are typically connected to a DC voltage source. Alternatively, anAC voltage source or a chopped DC or AC voltage source can be utilizedas the voltage source. Application of the voltage source to the lead-inrods causes the coil of wire to reach a temperature in excess of theignition temperature of the gas-air mixture which surrounds same causingthe ignition of the mixture. The use of a hot wire igniter, rather thana spark ignition device, permits the igniter to be used in very damp orwindy environments. Thus, the hot wire igniter of the present inventioncan be readily used within a gas grill that is stored outdoors. Inaddition, the operation of the hot wire igniter of the present inventionis not adversely affected by organic contamination from the foods thatare grilled since the surface of the hot wire igniter reaches atemperature that causes such contamination to be readily burned off andany leakage current resulting from organic contamination which wouldnormally absorb a high voltage spark and render it ineffective isinsignificant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the hot wire igniter of the presentinvention.

FIG. 2 is a front elevational view of the hot wire igniter of thepresent invention.

FIG. 3 is a right side elevational view of the hot wire igniter of thepresent invention; the left side elevational view being a mirror imageof this Figure.

FIG. 4 is a top plan view of the hot wire igniter of the presentinvention.

FIG. 5 is a bottom plan view of the hot wire igniter of the presentinvention.

FIG. 6 is a front elevational view of the heating coil utilized by thehot wire igniter of the present invention.

FIG. 7 is an end elevational view of the heating coil utilized by thehot wire igniter of the present invention.

FIG. 8 is a perspective view of a typical gas collector box containingthe hot wire igniter of the present invention and showing the attachmentof the gas collector box to a typical burner within a gas grill.

FIG. 9 is a perspective view of a typical gas collector box and showingthe attachment of the hot wire igniter of the present invention thereto.

FIG. 10 is an enlarged top plan view of a typical burner and a typicalgas collector box having the coil portion of the hot wire igniter of thepresent invention therein and showing the attachment of the gascollector box to the top surface of the burner.

FIG. 11 is an enlarged front elevational view of a typical burner and atypical gas collector box containing the coil portion of the hot wireigniter of the present invention therein.

FIG. 12 is a cross-sectional view of the burner and the gas collectorbox taken across section-indicating lines 12-12 in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the Figures where the illustrations are for the purposeof describing the preferred embodiment of the present invention and arenot intended to limit the invention described herein, FIG. 1 is aperspective view of the hot wire igniter 10 of the present invention.The hot wire igniter 10 is comprised of two (2) lead-in rods 12, a coil14 of wire whose opposite ends are each attached to one of the ends ofthe rods 12, an insulator member 16 and a mounting bracket 18.

The rods 12 are typically circular in cross-section, formed fromstainless steel, or the like, and are received within substantiallyparallel longitudinally extending bores (not shown) provided withininsulator member 16. The portions 20 of the rods 12 emanating from theend 22 of the insulator member 16 are usually swaged providing flatsurfaces for the attachment of electrical terminals (not shown). Inaddition, the swaged portions 20 of rods 12 are usually bent outwardlywith respect to one another permitting the easy attachment of theaforementioned electrical terminals. (Alternatively, the swaged portions20 of the rods 12 can be eliminated and the electrical attachmentthereto can be internal within the insulator member 16). The electricalterminals are connected to a power supply (not shown), such as a DCvoltage source. Alternatively, the power supply can be an AC voltagesource (not shown) or a chopped DC or AC voltage source (both notshown). The portions 24 of rods 12 emanating from the opposite end 26 ofinsulator member 16 are usually bent outwardly with respect to oneanother in order to provide a gap between the ends 28 thereof, as shownin FIG. 4. Each end 30 of coil 14 is welded to a rod 12 adjacent its end28 and the coil 14 is positioned so as to be recessed within the gapprovided between the ends 28 of the rods 12. As shown in FIGS. 2 and 3,the mounting bracket 18 includes a sleeve portion 32 which may have acompression member therein (not shown) to grippingly engage the outersurface of the insulator member 16. In addition, the mounting bracket 18has an aperture 34 therein, as shown in FIGS. 1, 4 and 5, permitting themounting of the igniter 10 within a collector box which is typicallyused in a gas grill that utilizes traditional spark ignition devices.Alternatively, the igniter 10 can be mounted directly to the burnerwithin the grill or can be attached to the grill through a mounting orattachment arrangement.

The coil 14 is formed from an iron, chromium, aluminum alloy wire whichcan be subjected to temperatures up to about 2,500° F. Alternatively,the coil 14 can be formed from platiniridium, which is an alloy ofplatinum and iridium, or a similar high temperature metal alloy. Thewire is typically 32 gauge or 0.008 inches in diameter and the centersection of the coil is tightly wound, as shown in FIG. 6. Typically, thecoil 14 includes about six full coil turns, however, a lesser number ofturns can be utilized. A minimum of two full coil turns is typicallyrequired to obtain the heat concentration that is provided by theadjacent coil turns. The coil turns typically have an outer diameter ofabout 0.052 inches which approximates the diameter of each rod 12. Whenformed, the coil turns usually do not touch one another and theoppositely disposed ends 30 of the coil 14 are substantially straightand concentric with the longitudinal axis of the coil turns but offsettherefrom so as to be positioned adjacent the outer radius of the coilturns. During the welding process, the coil 14 is oriented such that thecoil turns are positioned substantially above the oppositely disposedends 30 of the coil 14 in order to provide support and protection forthe coil turns after the coil 14 has been welded adjacent to the ends 28of the rods 12. During the conditioning and prove-in phase of theigniter 10, the coil 14 is heated by the application of a current sourcethereto for a pre-determined period of time annealing the coil 14 andcausing a protective oxide coating to form on the surface of the coil14. Through usage, the coil turns may contact one another. It should benoted that the protective oxide coating that forms on the outer surfaceof the iron, chromium, aluminum alloy wire utilized for coil 14 preventselectrical shorts if, because of coil sag and/or deformation due tousage and/or handling, adjacent coil turns touch one another duringoperation.

Suspending the coil 14 of wire between the rods 12 adjacent their ends28 may cause the coil 14 to sag and/or deform through usage. Thegeometry utilized for the coil 14 overcomes the problem of sag and/ordeformation. In the present invention, the outer turns of the coil 14heat the inner turns of same. The innermost coil turns typicallyexperience the hottest temperatures and are the ones most likely to sagand/or deform when heated. Through usage, the innermost turns of thecoil 14 may sag and/or deform but since these turns are of a relativelysmall radius, few in number, and are supported by the outer coil turns,the amount of sag and/or deformation is insignificant and, therefore,does not significantly affect the operation of the igniter 10. Anydeformation of the coil turns that may occur allows the gas-air mixtureto enter the gaps between adjacent turns to assist in the ignition ofthe gas-air mixture and compensates for any decrease in the operatingperformance of the coil 14 due to any increase in the electricalresistance of same through usage. It should be noted that the oppositelydisposed ends 30 of the coil 14 radiate and/or conduct a substantialportion of the heat contained therein to the surrounding air and to theends 28 of the rods 12 to which they are attached. By radiating and/orconducting such heat, the oppositely disposed ends 30 of the coil 14 areat a lower operating temperature than the coil turns, and thus,typically do not sag and/or deform. Because the heat is concentrated inthe innermost coil turns, any coil sag and/or deformation is minimizedand does not adversely affect igniter performance.

Referring now to FIG. 9, a perspective view of a typical gas collectorbox 40 showing the attachment of the hot wire igniter 10 of the presentinvention thereto is illustrated. The gas collector box 40 is comprisedof a housing 42 and a mounting bracket 44 attached thereto. An aperture46 is provided in the mounting bracket 44. Gas collector box 40 has anopening, shown generally by the numeral 48, thereto. The bottom surface50 of gas collector box 40 has an aperture (not shown) therein. The hotwire igniter 10 of the present invention is attached to the gascollector box 40 such that the portion of the insulator member 16adjacent the end 26 thereof is received within the aperture (not shown)in the bottom surface 50 of gas collector box 40 and a fastener 52 isreceived through aperture 34 in mounting bracket 18 to firmly attachmounting bracket 18 to bottom surface 50 of gas collector box 40. Inthis manner, the portions 24 of the rods 12 emanating from the end 26 ofinsulator member 16 and the coil 14 attached thereto are within the gascollector box 40 and adjacent the opening 48 thereto.

In order to mount the gas collector box 40 with the igniter 10 attachedthereto to a typical burner, the mounting bracket 44 is usually placedagainst the top surface 60 of the burner 62 in a gas grill 64, as shownin FIG. 8. A fastener 66 is then received within aperture 46 in mountingbracket 44 of gas collector box 40 to attach the gas collector box 40and the igniter 10 to the top surface 60 of the burner 62, as shown inFIG. 10. In this manner, the opening 48 to the gas collector box 40 isadjacent the outlet ports 68 in the bottom portion of the burner 62, asshown in FIGS. 11 and 12. Gas emanating from ports 68 in burner 62 isreceived through the opening 48 to the gas collector box 40 and mixeswith air therein permitting ignition of the gas-air mixture within thegas collector box 40 by the coil 14 of the igniter 10. The result isthat the gas emanating from ports 68 in burner 62 is ignited withinseveral seconds after power is applied to the igniter 10. It should benoted that the gas collector box 40 with the igniter 10 attached theretocan be mounted to the side surface or to the bottom surface of theburner 62, rather than to the top surface 60 thereof. Alternatively, theigniter 10 can be utilized without a gas collector box by mounting theigniter 10 directly to the burner 62 or to the body of the gas grillsuch that the coil portion thereof is adjacent to the outlet ports ofthe burner.

The hot wire igniter 10 of the present invention offers a number ofadvantages over presently available spark ignition systems for gasgrills. For example, the hot wire igniter 10 exhibits increasedresistance to moisture, especially in those situations where the grillis exposed to rain. In addition, any degradation in the operation of theigniter 10 due to organic contamination is not nearly as great as thatwhich occurs for spark ignition devices since the igniter 10 burns offany such contaminants and any leakage current that results from organiccontamination and which would normally absorb the high voltage spark,rendering it ineffective, is insignificant. The coil 14 within theigniter 10 is also resistant to mechanical shock and vibration since itis formed from a metal alloy, rather than a brittle ceramic-likematerial, and is protected because it is recessed between the ends 28 ofthe rods 12. Furthermore, the positioning of the wiring within the grillwhen utilizing the igniter 10 is not as critical as the positioning ofsuch wiring when a spark ignition device is utilized since the igniter10 utilizes a very low voltage which does not include a high frequencycomponent for operating purposes. Alternatively, an AC source or achopped DC or AC source of any voltage can be utilized. In addition,operation of the igniter 10 is virtually silent when compared with theoperation of spark ignition devices that typically utilize noisypiezoelectric elements to generate the required spark energy. Also, theigniter 10 is less expensive to produce than presently availableelectronic spark ignition devices and is more reliable than such devicessince it requires fewer parts. Lastly, the portion of the igniter 10that includes the coil 14 is readily receivable within a collector boxused for a spark ignition device permitting the easy replacement of sucha spark ignition device by the igniter 10.

Certain modifications and improvements will occur to those skilled inthe art upon reading the foregoing. It is understood that all suchmodifications and improvements have been deleted herein for the sake ofconciseness and readability, but are properly within the scope of thefollowing claims.

1) An igniter comprising an insulator member having at least twospaced-apart bores therethrough, at least two electrodes formed fromsolid metallic material, each of said electrodes being received withinone of said bores in said insulator member and being positioned thereinso that a portion thereof having a substantially circular cross-sectionprotrudes from an end of said insulator member, and a single strand ofsubstantially straight high temperature wire formed into a coil andattached to the exterior surface of the portions of said electrodesprotruding from said end of said insulator member. 2) The igniter asdefined in claim 1 wherein said single strand of substantially straightwire is formed from an iron, chromium, aluminum alloy. 3) The igniter asdefined in claim 1 wherein said single strand of substantially straightwire is formed from an alloy of platinum and iridium. 4) The igniter asdefined in claim 1 wherein said coil of wire includes at least two coilturns. 5) The igniter as defined in claim 4 wherein said coil turns areinitially in a spaced-apart relationship with respect to one another. 6)The igniter as defined in claim 4 wherein through usage said coil turnscontact one another. 7) (Canceled). 8) The igniter as defined in claim 1wherein the outer diameter of said coil of wire approximates thediameter of each of said electrodes. 9) (Canceled). 10) The igniter asdefined in claim 1 wherein said portions of said electrodes protrudingfrom said other end of said insulator member are swaged to accept in theattachment of a voltage source thereto. 11) The igniter as defined inclaim 1 further including a bracket member having an aperture therein,said insulator member being grippingly received within said aperture insaid bracket member. 12) The igniter as defined in claim 1 furtherincluding a gas collector box, said coil of wire and said portions ofsaid electrodes protruding from said end of said insulator member withsaid coil of wire attached thereto being received within said gascollector box and being positioned therein so as to ignite the gas-airmixture within said gas collector box. 13) The igniter as defined inclaim 12 wherein said gas collector box has an aperture therein for thereceipt of the portion of the said insulator member containing saidportions of said electrodes protruding from said end of said insulatormember with said coil of wire attached thereto. 14) The igniter asdefined in claim 12 wherein said gas collector box has an openingthereto permitting a gas-air mixture to be received therein. 15) Theigniter as defined in claim 12 wherein said gas collector box furtherincludes a mounting bracket attached thereto. 16) The igniter as definedin claim 15 wherein said mounting bracket attached to said gas collectorbox is attachable to the surface of a gas burner having outlet portstherein so as to position said gas collector box adjacent said outletports in said gas burner. 17) The igniter as defined in claim 1 furtherincluding a voltage source to supply power to said igniter. 18) Theigniter as defined in claim 17 wherein said voltage source comprises atleast one battery. 19) The igniter as defined in claim 17 wherein saidvoltage source is a DC voltage source. 20) The igniter as defined inclaim 17 wherein said voltage source is an AC voltage source.